1. Field
The presently disclosed subject matter relates to semiconductor light-emitting devices in which light emitted from a semiconductor light-emitting chip is wavelength-converted by a wavelength converting layer, and to manufacturing methods for the same. More particularly, the disclosed subject matter relates to semiconductor light-emitting devices for a vehicle light and the like, which can emit light having a high light-emitting density and efficiency from a small light-emitting surface, and to methods of manufacturing such devices.
2. Description of the Related Art
Semiconductor light-emitting devices, in which a part of the light emitted from a semiconductor light-emitting chip is converted into light having a different wavelength by a phosphor and in which a mixture light comprises the light having the different wavelength mixed with the light emitted directly from the light-emitting chip is emitted, have been used as a light source for various lighting units.
When the semiconductor light-emitting devices are used as a light source for a lighting unit such as a vehicle headlight, a projector, and the like, which controls light emitted from the light-emitting devices using a reflector and/or a projector lens, a light-emitting device having a small light-emitting surface may be desired to efficiently control light emitted from the light-emitting device with a small optical structure. For example, conventional semiconductor light-emitting devices, which reduce a planar light-emitting surface and a dome-shaped light-emitting surface, respectively, are disclosed in Patent Document No. 1 (Japanese Patent Application Laid Open JP2004-153277).
FIGS. 10a and 10b are side cross-sectional views showing the conventional semiconductor light-emitting devices disclosed in Patent Document No. 1. The conventional semiconductor light-emitting device 20 includes: a transparent substrate 25; a first conductive layer 26 located underneath the transparent substrate 25; a light-emitting region 28 emitting light located underneath the first conductive layer 26; a second conductive layer 32 located underneath the light-emitting region 28; a reflective contact layer 34 located underneath the second conductive layer 32; an optical cavity 35 located underneath the first conductive layer 26 and located adjacent the light-emitting region 28 and the second conductive layer 32; bumps 36 located underneath the reflective contact layer 34 and the optical cavity 35 to provide the first conductive layer 26 and the second conductive layer 32 with a driving current for the light-emitting region 28; and a ring-shaped reflective layer 22 located on a top surface of the substrate 25 so as to form a planar light-emitting surface 24 in a circular shape.
Accordingly, the semiconductor light-emitting device 20 can provide light emitted from a small light-emitting surface, which is the planar light-emitting surface 24 formed in a circular shape by covering the top surface of the substrate 25 with the ring-shaped reflective layer 22. The light-emitting device 20 also disclose a wavelength converting layer 21 located on the planar light-emitting surface 24 so as to be able to wavelength-converting light emitted from the light-emitting region 28.
However, as shown by a ray 30 in FIG. 10a, after many of the light rays emitted from the light-emitting region 28 may be reflected between the reflective layer 22 and the second reflective contact layer 34 and/or between the reflective layer 22 and the optical cavity 35 on several occasions, the light may finally be emitted from the planar light-emitting surface 24, which is formed in a small circular shape by the reflective layer 22. Therefore, a part of the light emitted from the light-emitting region 28 may decay while repeating reflections between the reflective layer 22 and at least one of the second reflective contact layer 34 and the optical cavity 35, and also may be absorbed in the light-emitting region 28, etc.
Accordingly, although the semiconductor light-emitting device 20 can emit light emitted from the small light-emitting surface 24, a light-emitting efficiency of the light may not necessarily be very high. Thus, in the conventional light-emitting device 20 it may be difficult to provide a wavelength-converted light having a high light-emitting efficiency and a high light-emitting density from the small light-emitting surface 24 via the wavelength converting layer 21.
Hence, as shown in FIG. 10b, a conventional semiconductor light-emitting device 20A is provided with a transparent dome 41, which is located wholly on the top surface of the substrate 25 so as to be able to receive almost all light emitted from the light-emitting region 28. The transparent dome 41 also includes a ring-shaped reflective layer 42 on a top surface thereof to form a small light-emitting surface, which is a dome-shaped light-emitting surface 44 formed in a circular shape in a top view from the device 20A by the reflective layer 42.
However, as shown by a ray 40 in FIG. 10b, many of the light rays emitted from the light-emitting region 28 may also be reflected between the reflective layer 42 and at least one of the second reflective contact layer 34 and the optical cavity 35 on several occasions, and the light may finally be emitted from the dome-shaped light-emitting surface 41, which is formed in a small circular shape by the reflective layer 22. Accordingly, a part of the light emitted from the light-emitting region 28 may decay while repeating reflections between the reflective layer 42 and at least one of the second reflective contact layer 34 and the optical cavity 35, and also may be absorbed in the light-emitting region 28, the transparent dome 41, etc.
In addition, a circular bottom surface of the transparent dome 41 may be difficult to completely cover the top surface of the substrate 25 formed in a square shape therewith, and therefore may be difficult to receive light emitted from a square light-emitting surface including four corners of the light-emitting region 28 at high efficiency. Thus, the conventional light-emitting device 20A may also be difficult to provide light having a high light-emitting efficiency and a high light-emitting density from the small light-emitting surface, even though the device 20A may form various small light-emitting surfaces.
Another conventional semiconductor light-emitting device having a small light-emitting surface and a high contrast between a light-emitting portion and a non-light-emitting portion may be used as a light source for a vehicle headlight, a projector and the like and is disclosed in Patent Document No. 2 (Japanese Patent Application Laid Open JP2010-157638). FIGS. 11a and 11b are a side cross-sectional view and a top view showing another conventional semiconductor light-emitting device, respectively, which is disclosed in Patent Document No. 2.
The conventional semiconductor light-emitting device 50 includes: a base board 53 having conductor patterns 54 on a mounting surface thereof; semiconductor light-emitting chips 51 mounted on the conductor patterns 54 of the base board 53, and each of chip electrodes thereof being electrically connected to a respective portion of the conductor patterns 54 via solder bumps 52; and a wavelength converting layer 55 mixing a wavelength converting material with a transparent material and disposed on a top surface of each of the light-emitting chips 51 so that an outside surface of the wavelength converting layer 55 are aligned with an outside surface of the light-emitting chips 51.
Additionally, the light-emitting device 50 includes; a first encapsulating member 56a including a light-reflecting material, the first encapsulating member 56a located around both the outside surfaces of the light-emitting chips 51 and the wavelength converting layer 55 and located between the adjacent light-emitting chips so as to encapsulate the semiconductor light-emitting chips 51 along with the mounting surface of the base board 54 and the wavelength converting layer 45; and a second encapsulating member 56b including a light-absorbing material.
The conventional semiconductor light-emitting device 50 can emit a wavelength-converted light from a small light-emitting surface via the wavelength converting layer 55, because the light-emitting surface of the conventional semiconductor light-emitting device 50 can become nearly equal to top surfaces of the light-emitting chips 51. In addition, light emitted from the both outside surfaces of the light-emitting chips 51 and the wavelength converting layer 55 may be reflected toward the wavelength converting layer 55 by the light-reflecting material included in the first encapsulating member 56a, and finally the light may be emitted from a top surface of the wavelength converting layer 55. Therefore, the conventional light-emitting device 50 may improve a light-emitting efficiency.
However, when a side surface of the first encapsulating member 56a is located perpendicular to the mounting surface of the base board 53 mounting the light-emitting chips 51 in the semiconductor light-emitting device 50 as shown in FIG. 11a, light reflected on the side surface of the first encapsulating member 56a, which contacts with the outside surface of the light-emitting chips 51, may return into the light-emitting chips 51. Accordingly, because an absorbing band of the light-emitting chips 51 may include a wavelength of the reflected light, the reflected light and an absorbing light may increase in the light-emitting chips 51.
Therefore, the increase of the reflected light and the absorbing light may cause a decrease in a total amount of light flux emitted from the conventional semiconductor light-emitting device 50. In addition, because light emitted from the top surface of each of light-emitting chips 51 may directly pass through the transparent material in the wavelength converting layer 55, the light may not enhance a light-emitting density. Thus, the conventional light-emitting device 50 may also be difficult to provide a wavelength-converted light having a high light-emitting efficiency and a high light-emitting density from the small light-emitting surface, although the device 50 may improve a contrast between the light-emitting portion and the non-light-emitting portion.
The above-referenced Patent Documents are listed below, and are hereby incorporated with their English abstracts in their entireties.    1. Patent Document No. 1: Japanese Patent Application Laid Open JP2004-153277    2. Patent Document No. 2: Japanese Patent Application Laid Open JP2010-157638
The disclosed subject matter has been devised to consider the above and other problems, features, and characteristics. Thus, embodiments of the disclosed subject matter can include semiconductor light-emitting devices that can emit a wavelength-converted light having a high light-emitting density and efficiency from a small light-emitting surface, and associated manufacturing methods that do not cause and/or are designed to prevent some of the above-described problems, concerns, and characteristics related to a wavelength converting layer. The disclosed subject matter can also include a semiconductor light-emitting device using a plurality of semiconductor light-emitting chips that can be used for wavelength-converting light having a high light-emitting density and efficiency from a small light-emitting surface.